Process for electrodeposition of metals under the influence of a centrifugal force field

ABSTRACT

THIS INVENTION RELATES TO THE ELECTRODEPOSITION OF METALS AND ALLOYS AND PROVIDES PROCESS AND APPARATUS FOR DEPOSITING METALS UNDER THE INFLUENCE OF A CENTRIFUGAL FORCE FIELD TO INCEEASE THE EFFECIENCY OF THE OPERATION AND PRODUCE METAL DEPOSITS HAVING A HIGH DENSITY AND MODULUS OF ELASTICITY.

flan 1974 l. AHMAD PROCESS FOR I'ILHCTRODEPOSITTON UE' METALS UNDER INFLUENCE OF A CFN'TRHUGAL FORCE FIELD Filed Dec 20, 1972 3 Sheets-Sheet l TO POWER SOURCE ATTORNEYS THE 15 Sheets-Sheet l. AHMAD INFLUENCE OF A CENTRIFUGAL FORCE FIELD 1 f l I 1 l I 1 l I I II PROCESS FOR BhIrIUTRODEPOSITlON U!" METALS UNDER 5mm. 22, WW

Filed Dec. 20, 1972 I I f l LLU I l. AHMAD 3,783,110 L'T TRODEPOSITION OF METALS UNDER THE A CENTRTFUGAL FORCE FIELD "Ian.- 1, 1974 INVENTOR Ifiul Ahmui "United States Patent O U.s. Cl. 204-12 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the electrodeposition of metals and alloys and provides process and apparatus for depositing metals under the influence of a centrifugal force field to increase the efliciency of the operation and produce metal deposits having a high density and modulus of elasticity.

This patent application is a continuation-in-part of applicants previously filed patent application Ser. No. 149,366, filed June 2, 1971, now abandoned, which was a continuation of patent application Ser. No. 792,683, filed J an. 21, 1969, now abandoned.

BACKGROUND OF THE INVENTION The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the electrodeposition of metals and alloys. In general, metals which are formed by electrodeposition, such as in the electroplating and electroforming processes, have various degrees of microporosity which reduces their properties of density and elastic modulus. Also, in the conventional modes of electrodeposition the efliciency of the operation is reduced, oftentimes considerably, due to various polarization effects.

SUMMARY OF THE *INVENTION It is a principal object of this invention to provide process and apparatus for the electrodeposition of metals and alloys whereby a greater degree of efficiency is achieved than has been realized before and the deposited metal is of a superior quality with respect to density and elastic modulus.

It is a further object of this invention to provide process and apparatus for the electrodeposition of metals which eliminate the adverse polarization effects that reduce the efiiciency of presently known means of electrodeposition.

It is another object of this invention provide process and apparatus for the electrodeposition of metals which deposit the metals at a higher rate than is possible with the prior art.

It is still another object of this invention to provide process and apparatus for the electrodeposition of metals under the influence of a centrifugal force field to increase the efliciency of the operation and the properties of the deposited metal.

It is another and still further object of this invention to provide process and apparatus for the electrodeposition of nickel from a sulphamate bath which is subjected to a centrifugal force field during electrodeposition.

Further objects and advantages of the invention will be apparent from the following specification and the accompanying drawings which are for the purpose of illustration only.

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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatus for forming metals by electrodeposition under the influence of a centrifugal force field;

FIG. 2 is an enlarged view taken along line 2-2 of FIG. 1;

FIG. 3 is a view taken along line 33 of FIG. 2 showing the electrolyte subjected to the centrifugal force field and displaced thereby from its normal level shown in phantom;

FIG. 4 is an enlarged, fragmentary view similar to FIG.

. 3 but of an alternate embodiment in which the cathode and anode are located in the same vertical plane;

FIG. 5 is a reduced view similar to 'FIG. 2 but shows the apparatus adapted for plating the outside of a cylinder; and

FIG. 6 is an enlarged view taken along line 6-6 of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS Oz./gal. Nickel sulphamate 43 Nickel as metal 10 Boric acid Nickel bromide (conc.) 7

Diluted to a specific gravity of 29-31 (Baum scale).

Cell 18 is rotated by a high speed motor 21 to produce centrifugal force field CF. The rate of rotation, and therefore the magnitude of centrifugal force field CF, is controlled by rheostat means 22 which is operationally disposed between motor 21 and a source of power not shown.

Shaft 24 of motor 21, to which cell 18 is mounted for rotation, extends axially into the cell and a disc 26 is mounted to such extending end 27, by means of an insulating connector 28, for simultaneous rotation therewith. Disc 26 is formed from copper as it is an excellent conductor of electricity, and is provided with an axial hub 29 having a well 30 extending downwardly thereinto to receive mercury pool 32.

Disc 26 carries three nickel anodes 34 which are disposed apart, as shown in FIG. 2, and are mounted, as noted at 36, for adjustable, radial displacement relative to the disc. Each anode 34 includes an arm 38 which supports an arcuate plate 40 at the outer end so that outer face 42 thereof is concentric to vertical wall 44 of cell 18, which is parallel to the extended axis of shaft 24. Mounted to the inside of wall 44 so as to be electrically insulated therefrom are three cathodes 46 which are disposed in radial alignment with anodes 34 and concentric therewith. Each cathode 46 is provided with an inner face 48 which is concentric with outer face 42 of anodes 34. A collector ring 50 is mounted to the inside of housing 16 and electrical connection is made between each cathode 46 and such ring by means of a carbon brush 52 which is displaceably mounted in a mount 53 so as to be spring-pressed against the ring. Each cathode 46 is provided with a cylindrical boss 55, FIG. 3 which extends through a hole in wall 44 and a mount 53 is threadingly engaged with the brush 52 and the cathode and also firmly hold the cathode to the wall. Mounts 53 and bosses 55 are, of course, insulated from wall 44.

DC current is supplied to anodes 34 and cathodes 46 from a source of power (not shown) through a regulator 54 which is adapted for adjusting the voltage and amperage output therefrom. Positive lead 56 from regulator 54 terminates in mercury pool 32 so as to apply a positive potential to anodes 34, through disc 26, during rotation of cell 18. Negative lead 58 from regulator 54 is connected to ring 50 so as to apply a negative potential to cathodes 46 through carbon brushes 52.

Demineralized water is added to electrolyte 20 from a reservoir 60 at a rate regulated by valve 62 to make up for evaporation loss.

Shown in FIG. 4 is an alternate embodiment of apparatus 12 in which anodes 64, which are counterparts of anodes 34, are mounted to wall 44 in substantially the same vertical plane as cathodes 46. In this embodiment, a channel 66 extends around each of the anodes 64 to form a pair of vertically spaced inner faces 68 thereon. Cathodes 46 are mounted within channels 66 so as to be insulated from the related anode 64, and boss 70 on each of the cathodes extends through the related anode and through wall 44 so that it can be threadingly engaged by a mount 53, as with the basic embodiment.

Electrical connection is made between positive lead 56 and each of the anodes 64 through the sliding contact of a carbon brush 72 related thereto with collector ring 74 mounted to the inside of housing 16. Each carbon brush 72 is displaceably disposed in amount 76 and is spring-pressed into contact with ring 74 which is connected to positive lead 56 and the mount is threadingly engaged with boss 78 of the related anode =64. Bosses 78 extend through wall 44, and are, of course, properly insulated therefrom.

Apparatus 12, as illustrated in FIGS. l-3, is prepared for operation by first cleaning anodes 34 and cathodes 46 by known practice and then mounting the cathodes to cell 18 and adjusting the position of the anodes relative to the cathodes to form a space therebetween. This space is determined in large part by the thickness of the nickel strip to be deposited on cathodes and the amount of electrolyte 20 necessary to fill the space when subjected to centrifugal force field CF. Electrolyte 20, at approximately 60 C. temperature, is then poured into cell 18 up to normal horizontal level L, shown in phantom in FIG. 3, which is a suflicient amount to cover faces 42 and 48 when the electrolyte is subjected to centrifugal force field CF. The sulphamate bath described hereinbefore has been used to good advantage as electrolyte 20 but the invention is not limited to this composition.

Motor 21 is then energized by adjustment of rheostat 22 to the desired speed which causes rotation of cell 18, with cathodes 46 attached thereto, and anodes 34. As cell 18 gains speed, electrolyte 20, under the influence of centrifugal force field CF, rises along wall 44, from its normal horizontal position L, to form a cylinder therealong and cover faces 42 and 48, as shown in FIG. 3. Current to anodes 34 and cathodes 46 is then turned on at regulator 54 which is adjusted for the desired current density and voltage potential. Experiments to date have been made with regulator 54 set at 40 amperes per sq. ft. and 2.5 volts although, because of the increased efficiency attainable as a result of this invention, deposition at a much higher current density is possible. With the rotation of cell 18, electrolyte 20 is not only subjected to centrifugal force field CF and an electrical force field it, together with the depositing ions therein, is moved relative to anodes 34 and cathodes 46.

When the metal deposited on cathodes 46 is of the desired thickness, the current is turned off at regulator 54 and rheostat 22. Cathodes 46 are then removed from cell 18 and the deposited strips of nickel removed therefrom. In these strips the porosity present in deposits produced by conventional methods and apparatus is minimized and the elastic modulus could approach the optimum value of 30x10 p.s.i. This is achieved in large part because the gas bubbles and liquid inclusions, which are entrapped in the deposit during the conventional forms of electrodeposition, are eliminated by the application of centrifugal force field CF to electrolyte 20 and the movement thereof along cathodes 46. Consequently, cell 18 must be rotated at a rate high enough to create a sufficient centrifugal force field CF and movement of electrolyte 20 relative to cathodes 46 to drive the bubbles and inclusions therefrom. A speed of at least 1500 rpm. is found to be adequate to achieve the unexpected result of eliminating gas bubbles to an extent to be effective. Particularly excellent results were obtained with rotation at 1817 r.p.m. When cell 18 is rotated at a higher speed it is expected that considerable changes in the structure of the deposit will take place due to the increased force applied to the depositing ions in electrolyte 20 and the increased rate of movement thereof relative to cathodes 46. Elimination of the bubbles and inclusions on cathodes 46, and the movement of electrolyte 20 therealong, also eliminates causes of the various polarization effects which, when present, reduce the efliciency of the electrodeposition. It has been found that at a particular current density the rate of deposition of the nickel is three times higher when cell 18 is rotated at 2500-3000 r.p.m. than when the cell is stationary. The same benefits from the process and apparatus of this invention can be achieved when applied to the electrodeposition of other metals and alloys.

Operation of apparatus 12, as illustrated in FIG. 4, is the same as that of the basic embodiment hereinbefore described.

Shown in FIGS. 5 and 6 is another embodiment of apparatus 12 wherein cell is adapted for plating the inside of cylinder 82. In this embodiment, top 84 of cell 80 is threadingly mounted on wall 86 thereof to permit insertion of cylinder 82 into the cell. Before cylinder 82 is inserted, a gasket 88 having the same diameter as the inside diameter of cell 80 is inserted thereinto and after the cylinder is placed on top thereof another gasket is placed on top of the cylinder. When top 84 is installed on wall 86 and tightened a seal is made between cylinder 82 and gaskets 88 and 90 to form a reservoir for electrolyte 20 when poured thereinto through opening 92 in top 84.

Electrical connection is made between negative lead 58 and cylinder 82, so that it will be made cathodic when current is applied thereto, by means of ring 50, and at least three carbon brushes 52 and mounts 53 therefor as described in the basic embodiment. In addition, provided for each mount 53 is a bushing 94, FIG. 5, with an external flange 96, which is mounted through a hole in wall 86 so as to be insulated therefrom and so that the flange is located on the inside of the wall. Each bushing 94 is provided with a threaded central bore 98 which is counterbored at 100 to slidingly receive a pad 102. Threaded portion 103 of mount 53 is received by bore 98 so as to act against pad 102, when tightened, to press the pad against the outside of cylinder 82. Together, bushings 94 cooperate, when tightened, to center cylinder 82 in cell 80, hold the cylinder against radial displacement, and provide electrical contact therewith.

Anodes 104 are similar to anodes 34 except that plates 106, which are the counterparts of plates 40, extend nearly the full length of cylinder 82. Suflicient space must be left between the top and bottom of plates 106 and therebetween as shown in FIGS. 5 and 6 to permit flow of electrolyte therethrough when cell 80 is energized for rotation. It is obvious that plates 106 may be connected to form a continuous cylinder with electrolyte 20, during displacement by centrifugal force field CF, flowing over and under the cylindrical anode. Operation is the same as that described for the basic embodiment.

I claim:

1. The process of forming by electrodeposition a substantially non-porous metal sheet characterized by an improved quality respective to density and modulus of elasticity, comprising the steps of:

mounting at least one metal collecting cathode in a rotatable cell concentrically around the outside of anode means radially spaced therefrom; placing a liquid electrolyte into said cell; rotating said cathode, anode means, and electrolyte simultaneously at a speed of at least 1500 r,p.m. to effect a centrifugal force in the direction from said anode means to said cathode at a speed sufijcient to eliminate gas bubbles from said electrolyte; applying an electrical current ,to said anode means and said cathode while rotating said cathode, anode means, and electrolyte; and removing said cathode after sufiicient electrodeposition of metal thereon, and stripping the sheet of collected metal from said cathode. 2. The process as defined in claim 1 wherein said metal layer formed by said electrodeposition is nickel.

3. The process of claim 2, including the step of increasing the rate of rotation of said cathode, anode means, and

electrolyte to at least 2500 revolutions per minute to thereby increase the rate of electrodeposition of the nickel metal at least 300 percent.

4. The process as defined in claim 1 wherein said cathode means, said anode means, and said electrolyte are rotated at a speed of 1817 revolutions per minute.

References Cited UNITED STATES PATENTS 644,029 2/1900 Cowper-Coles 204-212 X 875,784 1/1908. Cowper-Coles 204-412 895,163 8/ 1908 Cowper-Coles 204-2l2 X 1,858,125 5/1932 Von Devecis 204-213 X 3,359,195 12/1967 Hojyo 204-212 3,476,666 11/1969 Bell et a1. 204212 X 3,591,466 7/1971 Heiman 204216 X GERALD L. KAPLAN, Primary Examiner U.S. Cl. X.R. 

